1. Field of the Invention
This invention relates to a process for preventing lateral displacement of formed leads on integrated circuit packages. Such lateral displacement is hereinafter referred to as lead sweep. More particularly, it relates to such a process for preventing lead sweep in such packages which utilize etched lead frames. Most especially, it relates to such a process for preventing lead sweep in such packages which utilize "J" bends in the formed leads.
2. Description of the Prior Art
In the fabrication of integrated circuit packages, leads which are connected at their tips to the integrated circuit inside the package and extend outside the package for connection to the next level of packaging, such as a printed circuit board, are provided in lead frames during fabrication. The frame is cut away to leave the desired leads after assembly of the package. While the lead frames can be fabricated by a metal stamping operation, the technique of choice for low volume production, start up or development projects in the integrated circuit industry is to fabricate the lead frames by a double sided etching process. Such a process allows close control over dimensions of the resulting leads, especially at their narrow and closely spaced tips, where they attach to the integrated circuit. However, a problem encountered with such double sided etched lead frames is that the resulting leads tend to deform laterally when they are bent, such as to form the J bend conventionally employed with chip carrier packages. This lateral deformation or lead sweep causes misregistration of the leads on the integrated circuit packages when they are positioned for attachment to the next level of packaging. While this problem can be prevented by using stamped lead frames, such stamped lead frames are not suitable for many integrated circuit packages, due to excessive tooling cost or other considerations.